1. Field of the Invention
The present invention relates to an eye position detecting system, and more specifically to an eye position detecting system suitable for use in an automotive vehicle, to detect driver's inattentive driving due to a doze or looking aside.
2. Description of the Prior Art
The background of the present invention will be explained with respect to its application to the system used with an automotive vehicle.
As the first type of prior-art driver's eye position detecting systems for automotive vehicles, driver's eye position recognizing systems have been proposed as disclosed in Japanese Unexamined Published (Kokai) Pat. Appli. Nos. 60-158303, 60-158304, 61-77705 and 61-17706, in which an upper half of a driver face is irradiated with infrared rays emitted from two infrared stroboscopes; the reflected light is detected by two image sensors; two dark areas within the detected bright face image are extracted as two singular points; and the two extracted singular points are recognized as two eyes.
Further, as the second type of prior-art systems for automotive vehicles, an electric apparatus energizing control system has been proposed as disclosed in Japanese Unexamined Published (Kokai) Pat. Appli. No. 64-13491, in which the change in driver's eye conditions or the shape of driver's mouth speaking conditions is recognized to turn-on or off various electric apparatus such as buzzers, meters, automatic doors, relays, monitor TVs, etc.
In these prior-art eye position detecting systems, two eye existing areas are first decided before detecting eye positions. That is, a head top position of a driver face from a fixed position is detected in a face image: the detected face is divided into a few (e.g., three) areas; appropriate threshold values are determined for each areas respectively; and the lightness can be obtained as binary image signals to decide the eye existing areas.
In the first-type prior-art eye position detecting system, however, since the two dark areas within a closed bright area in a driver's face image are recognized as eye positions of singular points, when a half side of the driver's face is irradiated with direct sunlight, since the optical density (lightness) gradation on the driver face is excessively high and therefore is not uniformly detected, it is impossible to distinguish dark areas from bright areas so that eye positions cannot be detected.
Further, in the second-type prior-art eye position detecting system, when the external light conditions vary complicatedly during vehicle travelling, there exist various problems in that the driver's head position cannot be detected within the face image (being out of the detected image) so that the eye positions cannot be detected, and therefore the threshold levels must be adjusted many times according to the light density gradation in order to obtain binary image signals, thus resulting in slow response speed.
In summary, in the prior-art eye position detecting system, when the driver face is irradiated with direct sunlight, it has been difficult to accurately detect the driver eye position at high response speed and with high reliability.